Contact lens disinfecting and preserving solution

ABSTRACT

A disinfecting and/or preserving solution for contact lenses is disclosed. The solution is an aqueous solution containing 0.00001 to 0.1 weight percent of 1,5-pentanedial, optionally together with up to 0.004 weight percent of thimerosal or other enhancers and optional buffers and the like.

BACKGROUND

1. Field of the Invention

This invention relates to the use of 1,5-pentanedial as the activeantimicrobial agent in disinfecting and/or preserving solutions forcontact lenses.

2. Description of the Prior Art

This invention relates to disinfecting contact lenses, particularly softcontact lenses. When the term "soft contact lenses" is used herein, itis generally referring to those contact lenses which readily flex undersmall amounts of force and return to their original shape when releasedfrom that force. Typically, soft contact lenses are formulated frompoly(hydroxyethyl methacrylate) which has been, in the preferredformulation, crosslinked with ethylene glycol dimethacrylate. Forconvenience, this polymer is generally known as PHEMA. Soft contactlenses are also made from silicone polymers typically crosslinked withdimethyl polysiloxane. As is known in the art, conventional hard lensesusually consist of poly(methylmethacrylate) crosslinked with ethyleneglycol dimethacrylate.

Hard contact lenses do not absorb appreciable amounts of water as dosome soft contact lenses and thus the use of harsher disinfecting andcleaning agents does not create a problem in the hard contact lensescleaning area. However, many hard lens disinfecting and preservingsolutions contain benzalkonium chloride or chlorobutanol which mayrender the treated lenses hydrophobic, may not be stable in solution orlack compatibility with certain types of hard lenses, e.g., highsilicone content. As is generally known the users of soft contact lensesare warned against using solutions made for hard contact lenses sincethe materials in the solutions, as mentioned, may be absorbed or evenconcentrated by the soft contact lenses and may seriously damage thesoft contact lenses or the eye of the user.

U.S. Pat. No. 3,016,328, R. E. Pepper et al, discloses dialdehydealcoholic sporicidal compositions containing a saturated dialdehyde,e.g., glutaraldehyde, an alkanol and an alkalinating agent. Alsodisclosed are aqueous sporicidal compositions containing a dialdehyde(0.25 to 4%) and an alkalinating agent, the solution having a pH of 7.4or more. Medical, surgical and optical applications are suggested.

U.S. Pat. No. 3,697,222, G. Sierra, discloses the use of an aqueous acidglutaraldehyde solution at temperatures above 45° C. to sterilize anobject. The sterilizing action is enhanced by the use of ultrasonicenergy. Sterilization also may be achieved by using ultrasonic energyand aqueous alkaline glutaraldehyde solutions, the preferred temperaturebeing 55° to 65° C. Sierra teaches the aqueous glutaraldehydeconcentration can be up to 7.5% and preferably 1 to 2%.

U.S. Pat. No. 3,912,450 and U.S. Pat. No. 3,968,248, R. M. G. Boucher,disclose disinfecting or sterilizing medical items by contacting theitem with a sporicidal composition containing 0.1 to 5 weight percent ofglutaraldehyde and 0.01 to 1 weight percent of an ethoxylate typenon-ionic surface active agent and at a temperature of at least 15° C.Boucher discusses this development in some detail in an article (Amer.J. Hosp. Pharm. 31:546-547) published June 1974.

U.S. Pat. No. 3,968,250, R. M. G. Boucher, discloses disinfecting andsanitizing fowl eggs with an aqueous solution containing 0.1 to 5% ofglutaraldehyde and 0.01 to 1 percent of an ethoxylate type non-ionicsurface active agent.

U.S. Pat. No. 4,093,744, M. W. Winicov et al, discloses an aqueouscomposition containing 2 to 4 weight percent of glutaraldehyde and 0.1to 10 weight percent of a surfactant with a pH of 6.7 to 7.3 to killbacterial spores. This patent further discloses "Independent analyses ofthe sporicidal compositions disclosed in U.S. Pat. No. 3,016,328 toPepper et al revealed that the 10 hour contact kill time was readilyobtainable when using a fresh solution, but that the efficacy of thecompositions markedly decreased upon standing for prolonged periods ofup to about two weeks. Further, this reduction in effectiveness wasfound to be attributable to the diminution of glutaraldehyde, which losta total of about 25% of its by the end of a two week period."

Contact Lenses by Robert H. Hales, Williams & Wilkins Co., Baltimore, MD(1978) at page 33 records the use of glutaraldehyde as a chemicaldisinfectant for contact lens solution. While starting glutaraldehyde isa highly active bacterial and sporicidal agent, he notes it is toxic andirritating, unstable and requires an alkaline condition. No othermention is made of this antimicrobial agent.

SUMMARY OF THE INVENTION

In accordance with this invention, there is provided an aqueous solutionfor preserving and/or disinfecting contact lenses having as the activeantimicrobial agent 1,5-pentandeial present in an amount from about0.00001 to about 0.1 weight percent of said composition. Typically thesolution will be an isotonic solution and optionally contains enhancingor conditioning agents.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Applicants have discovered that contact lenses can be effectivelydisinfected and preserved with dilute aqueous solutions of1,5-pentanedial (popularly known as glutaraldehyde). More particularlyit was found that advantageous results are obtained when the1,5-pentanedial is present in an amount from 0.00001 to 0.1 weightpercent. Preferably the 1,5-pentanedial when used without an enhancer,which is hereinafter described, the concentration is from about 0.001 toabout 0.05 weight percent. When, in combination with an enhancer, the1,5-pentanedial antimicrobial agent of this invention can be present inan amount from about 0.00001 to about 0.01 weight percent and morepreferably from 0.0001 to 0.005.

The antimicrobial effect of 1,5-pentanedial can be enhanced or increasedby the use of an enhancer. An enhancer can be present in an amount fromzero to about 0.5 weight percent and preferably from about 0.0001 toabout 0.1 weight percent. Suitable enhancers are selected from the groupwhich includes thimerosal, phenylmercuric salts (e.g., nitrate, borate,acetate or chloride), sorbic acid, ethylenediaminetetracetic acid (EDTA)and its salts and mixtures of the foregoing enhancers. A particularlypreferred enhancer is thimerosal used in an amount from 0.0001 to about0.002 weight percent.

A typical composition of the present invention may contain, in additionto the active ingredients described earlier, buffers, cleaners,stabilizers and isotonic agents which aid in making the ophthalmiccomposition more comfortable to the user. These additional materialsmust be non-toxic and must not distort the lens.

Suitable buffers include sodium or potassium citrate, citric acid, boricacid, sodium bicarbonate and various mixed phosphate buffers includingcombinations of Na₂ HPO₄, NaH₂ PO₄ and KH₂ PO₄. Generally, buffers maybe used in amounts ranging from about 0.05 to 2.5 and preferably 0.1 to1.5% (w/v).

Non-ionic surfactants suitable for use as cleaners include neutralpolyoxyethylene fatty acid (available under the tradename Myrj 52),polysorbate 80 (tradename Tween 80) and polyethyleneglycol ether oflauryl alcohol (tradename Brij 35). These cleaners can be added inamounts ranging from 0.01 to 15 weight percent and preferably about oneweight percent.

The treating solution for soft contact lenses is typically maintained atan osmotic pressure similar to that of physiologic saline, i.e.,substantially isotonic, or equivalent to 0.9% saline, or with suitableagents alone or in combination to render the solution substantiallyisotonic. Hypotonic solution, e.g, tap water, may cause the lens toadhere tightly to the cornea while hypertonic solutions (excess saline)may result in stinging, lacrimation and a red eye.

The method of use of the solution comprises having the wearer of thesoft contact lenses remove the lenses from the eyes. Then the lenses arerubbed with preserved cleaning solution, rinsed with the preservedsaline solution and placed in a suitable container with a sufficientamount of the composition of the instant invention to cover the lenses.The lenses are allowed to soak preferably for period of from about 4hours to about 12 hours at room temperature. The lenses are then removedfrom the solution, washed with saline solution and then replaced on theeyes.

The following examples are illustrative only and should not be construedas limiting the invention. All parts and percentages referred to hereinare on a weight per volume basis. The saline solution used in theexamples is an isotonic, buffered saline solution unless otherwisespecified.

EXAMPLE I--Preserved Saline Solution

Isotonic saline solutions containing the indicated amounts of1,5-pentanedial and enhancer are prepared. Each solution is exposed toapproximately 1,000,000 microorganisms per ml of the indicated organism.The solution is considered effective if the concentration of Pseudomonasaeruginosa (ATCC No. 9027) is reduced to less than 0.1% of the initialconcentration within 14 days. In this example the enhancer used issorbic acid.

    ______________________________________                                                  Amount       Amount                                                           1,5-Pentanedial                                                                            Enhancer   Exposure                                    Solution  (Wt. Percent)                                                                              (Wt. Percent)                                                                            Result                                      ______________________________________                                        A          0.0025      --         ++                                          B          0.001       --         +                                           C          0.001       0.1        ++                                          D          0.0005      0.1        ++                                          E          0.0001      0.1        ++                                          F          0.00001     0.1        ++                                          G          0.000001    0.1        +                                           H          0.0000001   0.1        +                                           I          0.0005      --         NE                                          ______________________________________                                         ++ = Effective                                                                + = Marginal                                                                  NE = Not Effective                                                       

EXAMPLE II--Preserved Cleaner

A surfactant cleaner for lens cleaning and containing 0.1% of a neutralpolyoxyethylene fatty acid non-ionic surfactant (sold under thetrademark Myrj 52) by Atlas Powder Co.) is used in this comparison. Tothe cleaner is added the indicated amount of 1,5-pentanedial. Theeffectiveness against P. aeruginosa is determined as in Example I. Thesolution is considered effective against Candida albicans (ATCC No.10231) if its concentration remains at or below the initialconcentration of 1,000,000 microorganisms per ml for 14 days. Noenhancer is added to the cleaner.

    ______________________________________                                        Amount           Exposure Result                                              1,5-Pentanedial  (As in Example I)                                            Solution                                                                              (Wt. Percent)                                                                              P. aeruginosa                                                                             C. albincans                                 ______________________________________                                        A        0.0025      ++          ++                                           B        0.001       +           ++                                           C        0.005       *           ++                                           D        0.001       *           ++                                           E        0.0001      *           ++                                           F        0.00001     *           ++                                           ______________________________________                                          *Not Tested                                                             

EXAMPLE III--Disinfecting Solution

Isotonic disinfecting solutions for soft contact lenses are prepared inwhich the antimicrobial agent is 1,5-pentanedial. Some of the solutionsalso contain thimerosal as an enhancing agent. The prepared solutionsare exposed to approximately 1,000,000 microorganisms per ml for sixhours. The solution is considered effective if there is at least a 99.9percent reduction of the viable microorganism. The test microorganism isCandida albicans.

    ______________________________________                                                  Amount       Amount                                                           1,5-Pentanedial                                                                            Thimerosal Exposure                                    Solution  (Wt. Percent)                                                                              (Wt. Percent)                                                                            Result                                      ______________________________________                                        A          0.1         --         ++                                          B          0.05        --         ++                                          C          0.025       --         NE                                          D          0.005       0.002      ++                                          E          0.001       0.002      ++                                          F          0.0005      0.002      ++                                          ______________________________________                                         ++ = Effective                                                                = = Marginal                                                                  NE = Not Effective                                                       

EXAMPLE IV--Disinfecting Regimen

Two isotonic solutions, one containing 0.005 weight percent1,5-pentanedial and the other containing 0.003 weight percent1,5-pentanedial and 0.0002 weight percent thimerosal are evaluated in adisinfecting regimen for soft contact lenses. Both solutions are foundto be effective since the regimen completely removes from the lenses orkills the six pathogenic challenge organisms recommended by the U.S.Food and Drug Administration.

The foregoing examples and methods have been described in the foregoingspecification for the purpose of illustration and not limitation. Manyother modifications and ramifications will naturally suggest themselvesto those skilled in the art based on this disclosure. These are intendedto be comprehended as within the scope of this invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method for preservingor disinfecting soft contact lenses comprising contacting said lenseswith an aqueous solution having as the active antimicrobial agent1,5-pentanedial present in an amount from about 0.00001 to about 0.1weight percent of said composition, said composition being buffered foreye comfort (pH compatible) with at least one buffer in an amount fromabout 0.05 to 2.5 weight percent.
 2. The method of claim 1 wherein theamount of 1,5-pentanedial is from about 0.001 to about 0.05 weightpercent.
 3. A method of disinfecting contact lenses comprisingcontacting the lenses for a sufficient time to disinfect the lenses withthe aqueous solution of claim
 1. 4. A method of inhibiting microorganismgrowth when sterilized contact lenses are stored in a solutioncomprising storing the sterilized lenses in the aqueous solution ofclaim 1.